I figured this is the best board out there to ask this, so if you have any experience with this please help out. I have an FZJ80 front axle under my Land Rover, and its got bad death wobble. I did a cut and turn on this axle 9 months ago, and I put it to 7* Positive, with 315/75/16s. It has always had a slight death wobble at higher speeds and I am thinking it may be because I have too much caster. Anyone? Also, I know my front spring rate on my coilovers is too low, can this give death wobble? Bearings and alignment are spot on.

Start looking for loose steering components. ANY play at all is unacceptable. With the engine off have someone sit inside and "rock" the steering wheel slightly side to side while you look at each joint in the steering linkage. Again, ANY free play needs to be addressed.

Movement in the spring bushings, trackbar (if equipped), frame twisting/cracks all can contribute. Excessive backspacing on the wheels (too far out) junk tires, etc...

Do you have any pics the rig you can post?


Chris:cool2:

That is a lot of caster. I have never seen anything up to and including 2.5 ton trucks that had more than 3 degrees. While caster can contribute to wobble, zero caster is really bad. You need to have some slop in something that locates the wheel for it to get started. Get in there and shove and jerk stuff around and look for anything moving that shouldn't.

This probably gives us the best picture of what I'm dealing with.

http://i13.photobucket.com/albums/a290/TheDonJohnson/DSCN1559.jpg

As for play in the steering system, there is none. Brand new TRE's on the drag link, and new heims on the tie rod. The panhard rod heims are both perfect too. The only things I might suspect is the steering knuckle bearings could be too tigh (when I got this axle, there were no shims on the top cap?). But other than possibly that, there is nothing lose. What I was told by someone who seems pretty credible is that with 35" mud tires it is possible that the 7* of caster I have vs. say 3-4* can actually generate too strong of a force of the wheel wanting to fall back on itself (aka return to center) and this can actually bring upon shaking.

What I was told by someone who seems pretty credible is that with 35" mud tires it is possible that the 7* of caster I have vs. say 3-4* can actually generate too strong of a force of the wheel wanting to fall back on itself (aka return to center) and this can actually bring upon shaking.

I wouldn't believe 'em....my 55 has 8 degrees and doesn't shake one bit with 36" super swampers....

have you had it aligned professionally? does it have a bit of toe in?

can you move the tires any direction? Is it a tire wobble or a seat of the pants wobble?


bk

7 deg+ is allot, it may exaggerate the effect but I doubt that it is the cause.

IF you have no loose components,.........

have you checked toe in?

tires ballanced?

bent wheel?

BTW,.... can we get a pic of the knuckle and one of the panhard?

I don't have any pictures of the panhard rod setup, but it is exactly lined up with the drag link, I dont have bumpsteer, just death wobble.

Its a seat of the pants shake, rather frightening.

It was professionally aligned, toe at 0. Should I have it in a bit?

Since BKFJ55 has 8* and 36s I am beginning to think my caster cannot be causing this issue. My tires were balanced recently, but I think I'll go get them re-done and check for a bent rim too.

I have a pull to the left as well, and I think that it might relate to what I posted earlier about my springs. Ive got 14" coilovers and they were sold to me with a 250/300 spring combo, when really I think I should have a 300/350 combo. The truck weighs about 5700lbs. Also, one thing thats fucked up and I havent adressed yet is that I need to have 1.5" more preload on my pass. side shock to get the truck to sit level. Could my suspension being loaded up on that side be causing the death wobble?

Thanks for the info so far.

Just from the pic it does not look like there is 7* caster, it looks like it is neg caster or 0 at best.

i set up my mini truck axle with 1/8" to 1/4" toe in.

check out roger browns site for some good info and methods for alignment
http://www.4crawler.com/4x4/CheapTricks/AxleTech/index.shtml
(towards the bottom of the page)

Do you have positive or negitive caster? If the upper cap is further forward of the axle centerline you have negative caster, at 7deg that may be the problem. 7deg POSITIVE caster will add to the effort required to turn the wheel but shouldnt cause any wobble and the vehicle should track straight.

Any better pics of the knuckle area? I cant tell if the caster is neg or pos from the pic posted.


Chris:cool2:


Edit: How far away is the axle centerline from the steering arm where the tie rod connects? From the pic it looks like the steering box is too far forward. The tie rod from the steering arm to the steering box should be as close to parallel to the axle (within reason) as possible. Yours looks like 20-30deg forward.

all death wobble is frightening. Thus the name.

My 1st target is springs and ubolts. But dang, you don't have any!

Be thorough on everything! There is rarely a single consistent problem that causes death wobble. It could be anything, or a combination of anything.

Go over everything, and then again, and then again with a bigger cheater bar.

Good luck, keep us posted... oh, nice mod on the rover other than the wobble.

Just from the pic it does not look like there is 7* caster, it looks like it is neg caster or 0 at best.


Man, you must have good eyes :eek: How can you tell that by looking at the picture? I have about 7* caster on my SOA 40 and the only thing that has caused death wobble has been loose shackles and incorrect toe-in. I would still check the geometry though, just in case. I saw a cut and turn done once where the drivers side was rotated forwards, and the passenger side backwards - that would have been interesting to drive :laughing:

It does infact have 7* positive castor. That picture was taken before the cut and turn, I just posted it as a reference as its the only picture I have of the steering/suspension exposed.

As for the steering and panhard being angled out away from the axle. Thats how it was stock.

I have about 7* caster on my SOA 40 and the only thing that has caused death wobble has been loose shackles and incorrect toe-in.

Krusty, what toe in do you run?

so when your "death wobble" occurs, does the steering wheel shake or not? if not, then it might be coming from the rear.

is it a consistent and easily duplicated problem? could be a bent rim or axle shaft amongst many things.

so when your "death wobble" occurs, does the steering wheel shake or not? if not, then it might be coming from the rear.

is it a consistent and easily duplicated problem? could be a bent rim or axle shaft amongst many things.

Any time I go on the highway and try to push it over 60 it starts shaking. The steering wheel shakes. It is consistant.

Speaking of axle shafst, I'll check up on those and my spindles tomorrow.

Thanks for the help guys.

60mph is up there. most of the time, death wobble starts occuring at lower speeds.

here is a list of most of the things that could be wrong, most of them have been mentioned before:
1) caster
2) tow-in ; mostly lack thereof
3) bad TREs
4) bad suspension bushings/heims at axle or chassis ends
5) bad panhard angle and/or ends
6) loose/damaged wheel bearings
7) worn spindle surface where the bearing rides
8) loose/bad trunion bearings
9) loose steering arms
10) loose pitman arm
11) loose steering box
12) loose steering shaft joints
13) bad steering box
14) bent axle shaft
15) bent birf
16) bent spindle
17) bearing issue in wheel hub ( not concentric)
18) bent rim
19) tire issues
and i'm sure there's plenty more, but that list should be a good starting point. best of luck, hope you figure it out and please post up what you do figure out. :beer:

60 mph is not "death wobble" it occurs at lower speeds and gets worse until you either stomp the brakes or have the stupidity or balls to drive thru it.
I'd almost bet money you have tire/balance issues.
Slap some different tires on there off a rig that is smooth.
Butch

Death wobble is when you look out the window and the tires are flopping back and forth. At 60 MPH you would not survive without crashing. I have always seen it smooth out at 40 MPH. If...................I can get there without the thing coming apart.

I think you are experiencing a vibration different from death wobble.

60 mph is not "death wobble" it occurs at lower speeds and gets worse until you either stomp the brakes or have the stupidity or balls to drive thru it.
I'd almost bet money you have tire/balance issues.
Slap some different tires on there off a rig that is smooth.
Butch

Deeerrrrr, You callin' me stupid?? :homer:

I had death wobble at 40 before when I had a radius arm bushing go bad. This has the exact same feeling, and responds the same to braking and what not. Looks like Ive got my work layed out for me.

Deeerrrrr, You callin' me stupid?? :homer:


I gave you the choice.........of course some would argue having big brass balls is stupid.:p:p

Drive shafts out of balance/phase?

I been doing this for over 30 years

I'd bet money you have tire/balance issues.

Slap some different tires and wheels on there off a rig that is smooth.
Butch

I been doing this for over 30 years

I'd bet money you have tire/balance issues.

Slap some different tires and wheels on there off a rig that is smooth.
Butch


Agree 100% on the tire comment - its not death wobble at 60mph! You have tire/rim issues. Drive shafts cause vibration, not wobble, and this vibration often goes away at higher speeds.

In my case, my bias ply swampers are a serious contributor to death wobble as the form flat spots after sitting overnight - they tend to amplify the death wobble issues.

Good eyes, nope. But seen enough 80 axles to know that it looks like someone set the caster so the tie rod would clear the link set up. If that 80 arm is unbent from factory I would bet money that axle has 0 caster at best when sitting loaded. Maybe I'm tarded but I'll just bet if someone took a pic with a magnetic finder across the top trunion bolts it reads neg or 0 caster.